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Marine biodegradation mechanism of biodegradable plastics revealed by plastisphere analysis
Summary
Researchers analyzed the marine biodegradation mechanisms of two biodegradable plastics, PHBV and PBSA, by examining plastisphere functional gene assemblages, finding that differences in microbial community composition on their surfaces help explain why these polyesters degrade at substantially different rates in seawater.
Abstract Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(butylene succinate-co-adipate) (PBSA) are typical biodegradable polyesters; however, their biodegradability in the ocean differs substantially. Herein, we focused on functional genes correlated with biodegradation in ocean environments using multi-meta-omics approaches to identify the microbial groups and esterase enzymes correlated with biodegradation. Within the PHBV plastispheres, five Gammaproteobacteria were abundant, several of which encoded over 10 different types of extracellular poly(3-hydroxybutyrate (PHB) depolymerases that are highly expressed in the ocean. Within PBSA plastispheres, ecosystems of microbes formed on plastics, only two species of Gammaproteobacteria genomes were highly abundant and expressed: one for hydrolyzing PBSA and the other for consuming cleaved monomers. The high diversity of degrading microorganisms and enzymes could be related to the stable biodegradability of PHBV, while the low biodiversity of PBSA-degraders and necessity of symbiotic relationships likely characterize the instability of the marine biodegradability of PBSA. These results provide fundamental knowledge for the development of biodegradable marine plastics.